Furnace and method of using the same for reclaiming metal

ABSTRACT

A metal is vaporized in a lower chamber of the furnace by a lower heating mechanism and then is condensed by a condenser in an upper chamber of the furnace. The condenser subsequently is heated by an upper heating mechanism to melt the metal and allow the latter to flow downwardly from the condenser and to return to the lower chamber.

United States Patent [1 1 [4 1 Oct. 23, 1973 Bielefeldt 1 1 FURNACE AND METHOD OF USING THE SAME FOR RECLAIMING METAL [75] Inventor: Irvin P. Bielefeldt, Roscoe, 111.

[73] Assignee: Alco Standard Corporation, Valley Forge, Pa,

[22] Filed: July 28, 1971 [21] Appl. No.: 166,787

[52] US. Cl 75/63, 75/65, 266/15,

203/87 [51] Int. Cl. C22b 7/00, C22b 19/00, C21c 5/38 [58] Field of Search 75/63, 65, 88, 44,

[56] References Cited UNlTED STATES PATENTS 2,920,952 1/1960 Monson 75/1 3,484,233 12/1969 Bonilla 75/63 2,920,952 1/1960 Monson 75/1 3,632,334 1/1972 Quintin.... 75/63 1,994,358 3/1935 Holstein 75/88 3,226,314 12/1965 Wellington 75/178 2,816,814 12/1957 Plucknett... 23/294 3,360,362 12/1967 Davey 75/63 2,416,992 3/1947 Griswold 75/67 3,271,131 9/1966 Dickey 75/68 2,251,906 8/1941 Hanawalt... 75/67 2,949,495 8/1960 Caron 266/15 3,220,827 11/1965 Davey 266/15 3,136,627 6/1964 Caldwell 23/294 2,398,396 4/1946 Powell 203/87 Primary ExaminerL. Dewayne Rutledge Assistant ExaminerPeter D. Rosenberg Attorney-Wolfe, Hubbard, Leydig, Voit & Osann [57] ABSTRACT A metal is vaporized in a lower chamber of the furnace by a lower heating mechanism and then is condensed by a condenser in an upper chamber of the furnace. The condenser subsequently is heated by an upper heating mechanism to melt the metal and allow the latter to flow downwardly from the condenser and to return to the lower chamber.

4 Claims, 1 Drawing Figure PATENTED 0U 23 I913 vvmwrme: new/v e 5/525/16207} FURNACE AND METHOD OF USING THE SAME FOR RECLAIMING METAL BACKGROUND OF THE INVENTION This invention relates to a furnace for separating one metal from another by a vacuum distillation process in which the two metals are heated in a container to a temperature sufficiently high to vaporize the metal with the lowest vaporization point and thereby extract that metal from the other metal. The vaporized metal is condensed by and deposited on a condenser and is subsequently removed from the condenser for re-use.

SUMMARY OF THE INVENTION The primary aim of the present invention is to provide a new and improved furnace which may be used to carry out the above-described vacuum distillation process and which is uniquely constructed to enable removal of the metal deposited on the condenser in a simpler, easier and faster manner than has been possible heretofore.

A relatedobject is to provide a unique furnace which is capable of melting the condensed metal off of the condenser thereby to avoid the need of mechanically removing the metal from the condenser.

A more detailed object is to provide a furnace having lower and upper heated chambers for housing the container and the condenser, respectively, the lower chamber being used to vaporize the metal and the upper chamber subsequently being used to melt the condensed metal off of the condenser to enable such metal to flow downwardly and to return to the lower chamber.

The invention also resides in the novel method of extracting one metal from another and of removing the extracted metal from the condenser.

These and other objects and advantages of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS The single FIGURE schematically illustrates a new and improved furnace embodying the novel features of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT balt. After the components have deteriorated, they frequently are simply discarded because of the difficulty of reducing the carbide to particle size to enable subsequent re-sintering of the carbide. In some instances, the scrap has been mechanically crushed to reduce the carbide to particle size but this is costly as a result of the extreme hardness of the carbide and the subsequent processing involved. In other instances, the cobalt is separated from the carbide by chemical leaching. This process not only is comparatively expensive but also is detrimental to the maintenance of clean waterways since it ultimately is necessary to dispose of the chemicals used in the leaching operation.

There recently has been developed a carbide reclamation process which is more desirable from an ecological standpoint than leaching and which is less costly than either leaching or mechanical crushing. This process involves the roasting of the carbide scrap in the presence of zinc under high temperature conditions to cause the zinc to melt and form a eutectic alloy with the cobalt and thereby disintegrate the carbide mass. Subsequently, the zinc-cobalt alloy is subjected to vacuum distillation to vaporize the zinc and separate the latter from the cobalt. The vaporized zinc is deposited on and condensed by a condenser and later is removed from the condenser for re-use.

In accordance with the present invention, provision is made of a novel furnace 10 which is especially adapted for use in carrying out the above-described process and which is particularly characterized by its ability to automatically re-cycle the condensed zinc so that the zinc can be quickly and easily recovered for use in the roasting stage of a subsequent carbide reprocessing cycle. For this purpose, the furnace is formed with lower and upper chambers 13 and 14 equipped with independently operable heating mechanisms 15 and 16. During the roasting stage of each carbide re-processing cycle, the cemented carbide scrap and the zinc are heated by the lower heating mechanism 15 while being held in a container 17 in the lower chamber 13. After the zinc-cobalt alloy has been formed, the atmosphere in the chambers is evacuated to cause the zinc to vaporize and separate from the alloy, the vaporized zinc condensing and collecting on a condenser 19 located in the upper chamber 14. When the furnace has cooled, the container is emptied and re-filled with another batch of carbide scrap and, while the lower heating mechanism 15 is heating the new batch, the upper heating mechanism 16 is energized. to melt the condensed zinc from the condenser so that the zinc may flow downwardly off of the condenser and into the container for use in the next roasting stage. Accordingly, the present furnace l0 enables comparatively quick and easy recovery of the zinc extractedfrom the alloy and deposited on thecondenser.

More specifically, the furnace 10 (shown schemati- I cally in the drawing) includes a walled outer vessel 20 having a lower cover plate 21 adapted to be lowered away from the end of the vessel by an actuator 23 to permit access to the lower heating chamber 13. The lower and upper chambers 13 and 14 are defined within the vessel by insulated walls 24 of graphite felt. Felt partitions 25 span the vessel about midway between its ends and insulate the lower chamber from the upper chamber.

In this instance, the container 17 is a crucible which is supported on the lower cover plate 21 of the vessel 20. The lower heating mechanism 15 comprises electric resistance heating elements which are located in the lower chamber 13 adjacent the sides of the crucible 17. At its upper end, the crucible is formed with a tubular neck 27 which is telescoped slidably over a similar neck 29 depending from the condenser 19 and extending downwardly through the partitions 25. The condenser is located in the upper chamber 14 and comprises an outer casing 30 to which the neck 29 is connected. An additional neck 31 is connected to the upper end of the casing and extends upwardly toward the top of the vessel 16. Vertically spaced baffles 33 are housed within the casing to catch the vaporized zinc which rises from the crucible 17, the zinc striking against and condensing on the baffles. The baffles are staggered relative to one another so as to define an optical-tight, labyrinth path between the necks 29 and 31 and thereby insure that the zinc will strike the baffles.

The upper heating mechanism 16 is housed within the upper chamber 14 and also comprises a series of electric resistance heating elements which are disposed adjacent the outer sides of the condenser 19. The upper heating elements 16 may be energized independently of the lower heating elements and thus each of the chambers 13 and 14 may be heated either separately of or simultaneously with the other chamber.

In order to evacuate the atmosphere from the vessel when the zinc is vaporized, a vacuum pump 36 communicates with the vessel through a pipe 37 connected to the upper neck 31 of the condenser 19. To prevent oxidation of the zinc, the roasting stage of the process is carried out in the presence of a non-oxidizing atmosphere and, for this purpose, a non-reactive gas such as nitrogen or argon is adapted to be admitted into the vessel through a line 39 communicating with the lower chamber 13. Additional gas supply lines 40 and 41 communicate with the lower and upper chambers 13 and 14, respectively, and are connected to a blower 43 which is selectively operable to circulate cooling gas through a heat exchanger 44 and into the chambers, the cooling gas being returned to the heat exchanger through lines 46 and 47 communicating with the chambers 13 and 14.

In an exemplary carbide reclamation process, a batch of cemented tungsten carbide scrap and approximately an equal amount by weight of zinc are loaded into the crucible 17 which then is placed in the lower chamber 13. After the cover plate 21 has been sealed to the vessel 20, the latter is evacuated to remove the ambient air and then is backfilled with a non-reactive gas to at least atmospheric pressure and preferably to a pressure of several atmospheres. Thereafter, the lower heating elements 15 are energized to raise the temperature of the crucible to about l,500 F. The crucible is held at this temperature for approximately two hours and, during this time, the zinc melts and forms a eutectic alloy with the cobalt binder; The alloy thus formed infiltrates the matrix between the carbide particles and such infiltration expands the scrap and tends to split the carbide particles away from the cobalt so as to break the bond between the carbide and the cobalt.

Thereafter, the vessel 20 is evacuated to a pressure of about 50 microns and the temperature of the crucible 17 is raised to approximately 2,000 F. by the lower heating elements 15. At this temperature and pressure, the zinc vaporizes readily while the cobalt remains in liquid phase without re-sintering the carbide. During vaporization of the zinc, the upper heating elements 16 are not energized and thus the upper chamber 14 and the condenser 19 are relatively cool as compared to the lower heating chamber 13 and the crucible 17.

As the vaporized zinc rises out of the crucible 17, it passes into the condenser 19 and strikes the baffles 33 so as to condense and accumulate on the baffles. After about one hour, all of the zinc has been extracted from the crucible and deposited on the baffles and, at this time, the vessel 20 is backfilled with gas and is cooled so that the crucible can be removed from the lower chamber 13. With the bond between the carbide and the cobalt broken, the carbide scrap in the crucible is frangible and can be ball milled and subsequently formed into new tools.

After the processed scrap has been removed from the lower chamber 13, another batch of carbide is loaded into the chamber. Once the vessel 20 has been evacuated and backfilled, both the lower and upper heating elements 15 and 16 are energized simultaneously. The upper heating elements heat the condenser 19 and cause the zinc deposited on the baffles 33 to melt and to flow downwardly into the carbide-filled crucible 17. The zinc thus is returned to the crucible for re-use during roasting of the second batch of carbide. After all of the zinc has melted from the baffles, the upper heating elements 16 are de-energized and the upper chamber 14 is cooled preparatory to re-vaporization of the zinc. After several cycles, it may be necessary to add a small amount of additional zinc to the carbide in order to make up for any zinc which might be lost from the condenser 19.

From the foregoing, it will be apparent that the present invention brings to the art a new and improved furnace 10 which effects automatic recovery of the zinc deposited on the condenser 19. While the furnace has been described specifically in conjunction with a process for reclaiming cemented carbide scrap, it will be appreciated that the furnace may be used to advantage in various other processes in which one metal is extracted from another by vacuum distillation.

I claim:

1. In a furnace, the combination of, a walled vessel, a removable container in the lower portion of said vessel for holding a quantity of metal, an access opening in the lower portion of said vessel to permit said container to be inserted into and removed from said vessel, lower heating means in the lower portion of said vessel for melting and vaporizing part of the metal in said container, a condenser in the upper portion of said vessel and communicating with said container for collecting the vaporized metal and for condensing such metal into solid form, and upper heating means in the upper portion of said vessel for heating said condenser after the metal has been condensed thereon thereby to melt such metal and enable the the latter to flow downwardly from said condenser and back into said container, said lower heating means being energizable separately of said upper heating means.

2. In a furnace, the combination of, a walled vessel, an insulated partition dividing said vessel into upper and lower chambers, a removable container in said lower chamber for holding a quantity of metal, an access opening in the lower portion of said vessel to permit said container to be inserted into and removed from said vessel, means in said lower chamber for melting part of the metal in said container, a condenser in said upper chamber and communicating with said container through said partition, a vacuum pump communicating with the upper end of said condenser and communicating with said container by way of said condenser, said pump being operable to evacuate the atmosphere in said container to facilitate vaporization of said metal, said condenser including a plurality of baffles for collecting the vaporized metal and for condensing such metal into solid form, and upper heating means in said upper chamber and energizable separately of said lower heating means, said upper heating means being operable to heat said condenser after the metal has been condensed on said baffles thereby to melt such metal and enable the latter to flow downwardly from said condenser and back into said container.

3. A method of separating a first metal having a given boiling point from a second metal having a higher boiling point, said method comprising the steps of, placing said first and second metals in a chamber, heating said chamber first to form said metals into a molten alloy and then to raise the temperature of said alloy to a temperature above the boiling point of said first metal but below the boiling point of said second metal thereby to vaporize the first metal while leaving said second metal in molten form, collecting and condensing the vaporized first metal in solid form on a condenser located above said chamber, removing the second metal from the chamber, and heating the condenser to melt the first metal thereon and to cause such metal to flow back downwardly into said chamber.

4. The method defined in claim 3 in which said chamber is heated separately of said condenser when said first metal is vaporized and is heated simultaneously with said condenser when said first metal is melted on the condenser. 

2. In a furnace, the combination of, a walled vessel, an insulated partition dividing said vessel into upper and lower chambers, a removable container in said lower chamber for holding a quantity of metal, an access opening in the lower portion of said vessel to permit said container to be inserted into and removed from said vessel, means in said lower chamber for melting part of the metal in said container, a condenser in said upper chamber and communicating with said container through said partition, a vacuum pump communicating with the upper end of said condenser and communicating with said container by way of said condenser, said pump being operable to evacuate the atmosphere in said container to facilitate vaporization of said metal, said condenser including a plurality of baffles for collecting the vaporized metal and for condensing such metal into solid form, and upper heating means in said upper chamber and energizable separately of said lower heating means, said upper heating means being operable to heat said condenser after the metal has been condensed on said baffles thereby to melt such metal and enable the latter to flow downwardly from said condenser and back into said container.
 3. A method of separating a first metal having a given boiling point from a second metal having a higher boiling point, said method comprising the steps of, placing said first and second metals in a chamber, heating said chamber first to form said metals into a molten alloy and then to raise the temperature of said alloy to a temperature above the boiling point of said first metal but below the boiling point of said second metal thereby to vaporize the first metal while leaving said second metal in molten form, collecting and condensing the vaporized first metal in solid form on a condenser located above said chamber, removing the second metal from the chamber, and heating the condenser to melt the first metal thereon and to cause such metal to flow back downwardly into said chamber.
 4. The method defiNed in claim 3 in which said chamber is heated separately of said condenser when said first metal is vaporized and is heated simultaneously with said condenser when said first metal is melted on the condenser. 